1. Field of Invention
This invention relates to three and four component blends of ethylene vinyl alcohol copolymers, ionomer, and nylon (semicrystalline nylon in the three-component blend and semicrystalline and amorphous nylon in the four-component blend). These blends have a unique balance of properties and are useful in packaging films, laminates, co-extrusions and containers prepared therefrom. Also, the barrier resins of the present invention can be used as coatings on substrates such as paperboard and can be used in structures that are not multi-layer.
2. Background Discussion and Related Art
Ethylene/vinyl alcohol copolymers (EVOH), particularly those with high levels of vinyl alcohol, exhibit excellent oxygen barrier properties at low humidity. Typically, to provide good barrier properties at high humidities, EVOH is laminated on both sides with polyolefins (see U.S. Pat. No. 3,882,259 which is incorporated herein by reference). U.S. Pat. Nos. 4,952,628; 4,990,562; 5,003,002; 5,064,716; 5,110,855; 5,126,401; 5,126,402; 5,194,306; 5,208,082; and 5,286,575 (all of which are incorporated herein by reference) teach various blends of EVOH and amorphous nylon, and, in some cases, semicrystalline nylon with the amorphous nylon that have barrier properties less dependent on humidity. U.S. Pat. No. 4,082,854 which is incorporated herein by reference suggests a wide variety of polymers that can be blended with EVOH to improve gas permeation characteristics particularly for packaging applications.
In European Patent No. 0 470 486, entitled, "Toughened ethylene (vinyl alcohol) copolymer resins," which is incorporated herein by reference, the EVOH is blended with terpolymers of alpha-olefin, acrylate and either partly neutralized carboxylic acid groups or carbon monoxide. The combination is taught to have a combination of excellent oxygen barrier, toughness and thermoforming characteristics in the form of sheet or film.
It is also known that excellent properties such as gas-barrier, impact resistance, stretchability, drawability and transparency can result from blends of EVOH, ionomer and semicrystalline nylon (see Japanese Patent Application HEI6-310239, filed Dec. 14, 1994, to Kenji Miharu, inventor, which is incorporated herein by reference).